1. Field of the Invention
The present invention relates to a method for establishing the working mantime in the production line capable of impartially allocating jobs for various production means including workers or robots.
2. Description of the Prior Art
In most cases, in the flow production line, for example in an automobile assembly line, the workload for each process is set out so that the work of each process is completed in the period for flowing an automobile (called a "task"). As specifically, when desired to perform a work requiring mantime of 600 seconds, ten of work processes can be necessary.
By means of the standard time method, a production mantime is obtained such that the work is first classified in single tasks, and a plurality of time periods, each measured for each single task, are summed up. Thus, a production mantime is obtained. Specifically, at a task for integrally assembling two parts A and B by means of n pieces of bolts, if t1 to t5 are defined:
t1: the time necessary for transporting two parts A and B, PA0 t2: the time necessary for positioning these parts to each other, PA0 t3: the time necessary for tightening all bolts, PA0 t4: the time necessary for inspection, and PA0 t5: the time necessary for transporting completed products,
then, the total working mantime is obtained according to the equation: EQU t=t1+t2+t3.times.n+t4+t5 (1)
This total mantime is then divided by the numeral task T, to the result of which each is allocated.
In an automobile assembly line, for assembly of a vehicle, there are processes, such as mounting an engine to the main body, mounting doors and cooler pipes, and these processes are performed by one or a number of working means such as human workers and/or robots.
It is preferable if the workload is uniformly established for all the working means, especially in view of uniform wear of components without loading on parts of a particular positions. In most cases, a mantime calculated using the standard time method is allocated for workers. However, inequity is often likely to occur if only using the mantime obtained by the standard time method.
For instance, even in the task for tightening bolts with the same torque and the same length, the task at a narrow position requires a workload greater than usual, while an additional tightening task rather requires a load smaller than usual.
A production process comprises a plurality of elementary tasks. Among these tasks, those with fatigue greater than the predetermined workload, such as, tasks with hard posture, difficult tasks, or heavy weight tasks, are often included. The fatigue extent of these tasks cannot be represented by means of the conventional standard time method. When the tasks are allocated using this method, there can be caused inequity between workers.
Further, even if the method above is properly applied, fatigue produced by using a specific portion of the worker can be caused, such that a robot is entirely wasted only by being wasted of merely part of components of the robot.